Effect of age-related extended high frequency hearing loss on the subjective impressions of dental drill noise

Yamada T., Kuwano S., Ebisu S., et al. Effect of age-related extended high frequency hearing loss on the subjective impressions of dental drill noise. Scientific Reports 14, 15655 (2024); https://doi.org/10.1038/s41598-024-65429-y.Fear and anxiety among patients are sometimes evoked in dental clinics due to the sound of dental drills. This study aimed to explore the impact of age-related hearing loss in the extended high frequency (EHF) range above 8 kHz on individuals' subjective discomfort towards dental drill noise. After measuring pure-tone audiometric thresholds at both conventional and extended high frequencies, we used a psychoacoustic approach to evaluate subjective impressions of four dental drill sound stimuli, which featured varying frequency components, in 62 participants (aged 12–67 years). We found a significant decrease in hearing sensitivity within the EHF range as age increased, with notable differences in hearing thresholds at 14 kHz between teenage and older adults exceeding 65 dB. Furthermore, significant differences were observed between younger and older (above 40 years) participants in the subjective impressions of dental drill noise, emphasizing age as a critical factor in the perception of high frequency components. Consequently, age may influence the unpleasantness of dental drilling noise. Compared to older individuals, young participants may exhibit increased fear of dental procedures owing to physiological factors. These results underscore the need for age-appropriate noise control strategies in dental clinics to mitigate anxiety and improve patient comfort

Equilibrium dialysis and carborydrate-binding studies on the 2-acetamido-2-deoxy--glucopyranosyl-binding lectin from bandeiraea simplicifolia seeds

The carbohydrate-binding specificity of Bandeiraea simplicifolia lectin II (BS II lectin) has been studied by quantitative precipitin and hapten-inhibition analysis. The BS II lectin precipitated biopolymers having nonreducing 2-acetamido-2-deoxy--glucopyranosyl residues, such as antigen A. Dextran B-1355-S and rabbit-liver glycogen also afforded precipitin curves with high concentrations of the BS II lectin. Phenyl 2-acetamido-2-deoxy-[alpha]--glucopyranoside and p-nitrophenyl 2-acetamido-2-deoxy-[alpha]--glucopyranoside, the best inhibitors of the BS II lectin-p-azophenyl 2-acetamido-2-deoxy-[beta]--glucopyranoside-bovine serum albumin conjugate precipitin-system, were 4 times as active as 2-acetamido-2-deoxy--glucopyranose. Of the free monosaccharides tested, 2-acetamido-2-deoxy--glucopyranose was the most potent inhibitor, being over 100 times better than -fructose and 400 times better than -glucose. Comparison of the inhibiting capacity of methyl or p-nitrophenyl 2-acetamido-2-deoxy-[alpha]--glucopyranoside with their corresponding [beta] anomers showed that the [alpha] anomer was bound 6 to 8 times more avidly than the [beta] anomer. Replacement of the C-3, C-4, or C-6 hydroxyl group of -glucose by a methoxyl group or a fluorine atom abolished the capacity of the resulting sugar to bind the BS II lectin, but substitution of the C-2 hydroxyl group of -glucose, by either a methoxyl group or a fluorine group, had no appreciable effect on binding to the lectin. N,N'-Diacetylchitobiose was as active as N,N',N"-triacetylchitotriose, and they were both twice as potent as disaccharides having a nonreducing 2-acetamido-2-deoxy-[beta]--glucopyranosyl residue. Disaccharides having [beta]--(1 --> 6) glycosidic bonds were very poor inhibitors. Equilibrium-dialysis experiments with p-nitrophenyl 2-acetamido-2-deoxy-[alpha]--glucopyranoside as binding ligand indicated that the BS II lectin possesses approximately one carbohydrate-binding siteper subunit for the tetrameric protein (Mr 113,000), with association constants of 1.3 x 105 M-1 at 4[deg], and 0.4 x 105 M-1 at 37[deg].Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22639/1/0000190.pd

Equilibrium dialysis and carbohydrate-binding studies on the 2-acetamido-2-deoxy--glucopyranosyl-binding lectin from Bandeiraea simplicifolia seeds

The carbohydrate-binding specificity of Bandeiraea simplicifolia lectin II (BS II lectin) has been studied by quantitative precipitin and hapten-inhibition analysis. The BS II lectin precipitated biopolymers having nonreducing 2-acetamido-2-deoxy--glucopyranosyl residues, such as antigen A. Dextran B-1355-S and rabbit-liver glycogen also afforded precipitin curves with high concentrations of the BS II lectin. Phenyl 2-acetamido-2-deoxy-[alpha]--glucopyranoside and p-nitrophenyl 2-acetamido-2-deoxy-[alpha]--glucopyranoside, the best inhibitors of the BS II lectin-p-azophenyl 2-acetamido-2-deoxy-[beta]--glucopyranoside--bovine serum albumin conjugate precipitin-system, were 4 times as active as 2-acetamido-2-deoxy--glucopyranose. Of the free monosaccharides tested, 2-acetamido-2-deoxy--glucopyranose was the most potent inhibitor, being over 100 times better than -fructose and 400 times better than -glucose. Comparison of the inhibiting capacity of methyl or p-nitrophenyl 2-acetamido-2-deoxy-[alpha]--glucopyranoside with their corresponding [beta] anomers showed that the [alpha] anomer was bound 6 to 8 times more avidly than the [beta] anomer. Replacement of the C-3, C-4, or C-6 hydroxyl group of -glucose by a methoxyl group or a fluorine atom abolished the capacity of the resulting sugar to bind the BS II lectin, but substitution of the C-2 hydroxyl group of -glucose, by either a methoxyl group or a fluorine group, had no appreciable effect on binding to the lectin. N,N'-Diacetylchitobiose was as active as N,N'N''-triacetylchitotriose, and they were both twice as potent as disaccharides having a nonreducing 2-acetamido-2-deoxy-[alpha]--glucopyranosyl residue. Disaccharides having [beta]--(1 --> 6) glycosidic bonds were very poor inhibitors. Equilibrium-dialysis experiments with p-nitrophenyl 2-acetamido-2-deoxy-[alpha]--glucopyranoside as binding ligand indicated that the BS II lectin possesses approximately one carbohydrate-binding site per subunit for the tetrameric protein (Mr 113,000), with association constants of 1.3 x 105 M-1 at 4[deg], and 0.4 X 105 M-1 at 37[deg].Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22640/1/0000191.pd

Synergistic effects of arginine and fluoride on human dental biofilm control

Kuriki N., Asahi Y., Okamoto M., et al. Synergistic effects of arginine and fluoride on human dental biofilm control. Journal of Dentistry 149, 105307 (2024); https://doi.org/10.1016/j.jdent.2024.105307.Objectives: The aim of this study was to quantitatively and comprehensively investigate the combined effects of arginine and fluoride on the suppression of pathogenicity using an in situ biofilm model and next-generation sequencing (NGS). Methods: Using the in situ model, dental biofilms were formed and the viable bacterial counts and arginine activity in the arginine- and fluoride-containing dentifrice and control groups were measured. We also compared their effects on the bacterial microbiota and predictive functional factors in the control, arginine (arg), and arginine + fluoride (argF) groups using NGS analysis. Results: Compared to the control treatment, the use of 8 % arginine and 1450 ppm fluoride toothpaste resulted in significantly high oral NH4+ concentrations without affecting the number of viable bacteria (P < 0.05). NGS analysis revealed that the oral microbiota of the control, arg, and argF groups were significantly different. Heat map analysis of the predicted functional factors revealed that the arg group had different properties from the other groups and activated specific substrate metabolic pathways; contrastingly, argF treatment inhibited the activity of these pathways and prevented an increase in the abundance of bacterial genera that utilize substrates such as sucrose, suggesting the synergistic effect of arginine and fluoride. Conclusions: This study indicates that the combination of arginine and fluoride has a synergistic effect on the bacterial microbiota and pathogenicity of dental biofilms compared with arginine alone. Clinical significance: Our findings suggest that the combination of arginine and fluoride could be used as an effective prebiotic and may inhibit the growth of bacteria associated with dental diseases

Root canal treatment with high-frequency waves in rats

The purpose of this study was to develop a high-frequency wave therapy model in rats and to investigate the influence of high-frequency waves on root canal treatment, which may provide a novel strategy for treating apical periodontitis. Root canal treatments with and without high-frequency wave irradiation were performed on the mandibular first molars of 10-week-old male Wistar rats. The mesial roots were evaluated radiologically, bacteriologically, and immunohistochemically. At 3 weeks after root canal treatment, lesion volume had decreased significantly more in the irradiated group than in the non-irradiated group, indicating successful development of the high-frequency therapy model. The use of high-frequency waves provided no additional bactericidal effect after root canal treatment. However, high-frequency wave irradiation was found to promote healing of periapical lesions on the host side through increased expression of fibroblast growth factor 2 and transforming growth factor-β1 and could therefore be useful as an adjuvant nonsurgical treatment for apical periodontitis

Assessment of the functional efficacy of root canal treatment with high-frequency waves in rats

The purpose of this study was to develop a high-frequency wave therapy model in rats and to investigate the influence of high-frequency waves on root canal treatment, which may provide a novel strategy for treating apical periodontitis. Root canal treatments with and without high-frequency wave irradiation were performed on the mandibular first molars of 10-week-old male Wistar rats. The mesial roots were evaluated radiologically, bacteriologically, and immunohistochemically. At 3 weeks after root canal treatment, lesion volume had decreased significantly more in the irradiated group than in the non-irradiated group, indicating successful development of the high-frequency therapy model. The use of high-frequency waves provided no additional bactericidal effect after root canal treatment. However, high-frequency wave irradiation was found to promote healing of periapical lesions on the host side through increased expression of fibroblast growth factor 2 and transforming growth factor-β1 and could therefore be useful as an adjuvant nonsurgical treatment for apical periodontitis.Assessment of the functional efficacy of root canal treatment with high-frequency waves in rats. Saori Matsui, et al. PLOS ONE. 2020.9(29) doi.org/10.1371/journal.pone.023966

Key factors in achieving firm adhesion in post–core restorations

Adhesive post–core restorations using a combination of fiber reinforced posts (FRPs) and resin composites have become the preferred choice worldwide in restoring pulpless teeth. The success of this method, especially because of the low incidence of root fracture, has been shown in many clinical studies in several countries. However, the method has also shown a tendency for the FRP to come detached from its post-space, and this potential flaw raises questions about the long-term durable prognoses of such restorations. The adhesive characteristics of post–core materials to root canal dentin have been widely investigated as part of the attempt to find a solution to the problem. Comprehensive understanding of the way that root canal dentin behaves in the post-space may be the key to achieving their better adhesion. Clinicians have to contend with the high stresses produced in the post-space because of its extremely high C-factor. When using light-cured and even dual-cured materials, ensuring deep and complete light penetration is essential to obtain even bonding strength throughout the post-space. Chemically cured adhesive materials, where the progress of curing is relatively slow and there is less stress caused by polymerization shrinkage, should be positively considered for the root canal bonding. In every case, careful attention needs to be paid to the negative effects that endodontic irrigation solutions, such as sodium hypochlorite and EDTA, have on root canal adhesion. Even after better adhesion of the FRP to root canal dentin has been achieved—and proved by high-quality long-term clinical studies, the concept of cusp-coverage in pulpless molars may need to be reconsidered based on a good conservative policy of minimal intervention

Interaction of pneumococcal S-14 polysaccharide with lectins from Ricinus communis, Triticum vulgaris, and bandeiraea simplicifolia

Two purified lectins, namely, wheat-germ agglutinin (from Triticum vulgaris) and the hemagglutinin from Ricinus communis seeds, readily form a precipitate with pneumococcal S-14 polysaccharide, whereas the Bandeiraea simplicifolia lectin (BS 1) does not. Exhaustive periodate oxidation and borohydride reduction of S 14 modifies terminal [beta]--galactopyranosyl residues, as well as chain -glucopyranosyl residues, and abolishes reactivity with both the R. communis lectin and wheat-germ agglutinin. Controlled periodate oxidation followed by Smith degradation cleaves only terminal [beta]--galactopyranosyl residues, giving a linear polymer, the structure of which was determined by methylation analysis. This derived polymer, containing (1--&gt;6)-linked 2-acetamido-2-deoxy-[beta]--glucosyl residues, readily precipitated wheat-germ agglutinin, but not the R. communis lectin.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22848/1/0000409.pd

Assessment of Inhibitory Effects of Fluoride-Coated Tubes on Biofilm Formation by Using the In Vitro Dental Unit Waterline Biofilm Model▿

This study aimed to establish an in vitro model to simulate biofilms formed in dental unit waterlines (DUWLs) and to investigate the ability of polyvinylidene fluoride (PVDF)-coated tubes to inhibit biofilm formation using this model. The water and biofilm samples were obtained from DUWLs which had been clinically used for 2.5 years, and the predominant bacteria were identified. A conventional polyurethane tube was incubated for 24 to 96 h in the mixed flora of isolated bacteria, and the optimal incubation conditions to simulate a clinically formed biofilm were determined by observation with a scanning electron microscope. Biofilm formation on a PVDF-coated tube was observed using this in vitro model, and the adherence of different bacterial species to conventional and PVDF-coated tubes was assessed. Sphingomonas paucimobilis, Acinetobacter haemolytics, and Methylobacterium mesophilicum were predominantly isolated from contaminated DUWLs. Incubation of the polyurethane tube with the mixed flora containing these three species for 96 h resulted in the formation of a mature biofilm similar to the one clinically observed. The PVDF-coated tube was significantly less adhesive to all three bacterial species than the polyurethane tube (P < 0.05 by the Mann-Whitney U test), and the attachment of small amounts of rods was observed even after incubation with the mixed flora for 96 h. In conclusion, an in vitro biofilm model was obtained by using a mixed flora of bacteria isolated from DUWLs, and the PVDF-coated tube was found to be effective in preventing biofilm formation using this model